Lithologic variations in otago schist, mt aspiring area, northwest otago, new zealand

Abstract

Psammitic schist, 2 types of pelitic schist (grey and porphyroblastic), and 4 types of greenschist (metavolcanic rock — light, spotted, foliated, and epidote rich) are recognisable on outcrop scale in textural zone 4 of the Otago Schist, northwest Otago, New Zealand. Thin horizons of metachert, marble, and ultramafic rock are commonly associated with greenschist. Broad units with 1 predominant rock type (greenschist, psammite, grey pelite, or porphyroblastic pelite) are mappable on a regional scale. These units also contain most or all of the above rock types and have poorly defined boundaries. The degree of original Stratigraphic continuity within and between these broad units is unknown. The studied area can be subdivided into 2 lithologic associations, the “Aspiring association” and the eastern “Wanaka association”, separated by a north-trending, poorly defined but lithologically gradational boundary. The Aspiring association is made up predominantly of pelitic rock types with considerable quantities of greenschist and minor marble, chert, and ultramafic horizons. The Wanaka association consists of psammitic schist with subordinate greenschist and pelitic schist. The proportion of greenschist decreases eastwards. These “associations” represent fundamental lithologic differences within the Otago Schist belt, on a scale equivalent to the previously defined Te Anau Assemblage. © 1984 Taylor & Francis Group, LLC.